1. Field of the Invention
This invention relates to a cleaning method and apparatus for removing liquid substance such as water, oil or the like and/or solid substance such as zincing or the like which is adhered to the surface of an object. It also concerns a method and an apparatus for efficiently recovering substance such as plated material adhered to the surface of an object to be processed, by causing such materials to be evaporated in a vacuum.
2. Description of the Prior Art
Such procedures as pickling, shot-working, and in-air oxidation removal have heretofore been well known in the art as methods of removing zincing provided on the surfaces of an automobile body, for example.
Of such conventional methods, pickling is most commonly employed, but it is disadvantageous in that the cleaning liquid used therewith tends to cause environmental pollution and also in that the running cost is high and skilled workers are needed. Shot-working also has such disadvantages that the running cost is high and difficulties are experienced in processing shot-particles having zinc adhered thereto. Further, the in-air oxidation removal procedure is disadvantageous in that oxide tends to be formed on the object to be processed per se and the dezincing ability is poor. Thus, in the case where iron plate is melted for recycling, unmelted material such as iron oxide, zinc oxide or the like and/or zinc is caused to infiltrate into the wall of the furnace so that the life span of the furnace tends to be shortened.
Also well known in the art is a method of recovering zinc, nickel and/or lead adhered to the surface of an automobile body and/or oil adhered thereto, by increasing the temperature of the vacuum atmosphere in which such a body is placed. However, due to the fact that no convection-heating means is provided, such conventional method is disadvantageous in that the temperature increasing rate in the range of 0.degree. to 500.degree. C. is extremely low; thus, when it is attempted to effect dezincing of 6,000 tons of scrap per month, a large-sized equipment is inevitably required so that the cost merit is lost because of its high initial cost. To cope with such problems, it may be conceivable that oxidation-heating is effected during the low-temperature period while vacuum-heating is carried out during the evaporation period. With such a procedure, however, metal oxide is formed so that the vacuum-evaporation temperature should be elevated as a matter of course; thus, to completely remove the zincing, the temperature should be elevated for a long period of time. In this case, too, the cost merit is lost as in the above-mentioned cases.
As mentioned above, the prior-art method is disadvantageous in that the temperature rising rate of the conventional vacuum furnace is low; heating with inert gas such as nitrogen gas or the like is high in running cost; oxidation-heating requires that the evaporation temperature be elevated so that the evaporation rate turns out to be slow, which has adverse effect on the running cost or the like.